A cylindrical water tank 1.5 m in diameter and 2.5 m high is surrounded on both ends and the sides with RSI =3 insulation. It is desired to keep the water at 80 degrees C, while the ambient temperature is 20 degrees C. WHat is the minimum RSI- value that is required for the walls and roof?
Ans) Given,
Diameter of tank = 1.5m
Height of tank = 2.5m
RSI value of material surrounding tank = 3
Temperature difference (T) = 80 - 20 or 60oC
Minimum RSI value required = Surface area x T / Heat loss per hour
Given that tank is surrounded with RSI 3 material at wall and both ends
Total area = dh + 2 x(/4) d2
= 15.30 m2
therefore,
3 = 15.30 x 60 /heat loss
heat loss = 306 W
Surface area of wall and roof = dh + (/4)d2
= (3.14)(1.5)(2.5) + (3.14/4) x1.5x1.5
= 13.55 m2
Minimum RSI value required = 13.55 x 60 / 306
= 2.65 m2oC /W
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